Pneumatic control apparatus



April 1953 y .c.B. MooRE PNEUMATIC CONTROL APPARATUS Filed Nov. 16, 1948 INVENTOR.

CO LEMAN MQQE 14A .TQ v

ATTORNEY Patented Apr. 21, 41953 PNEUMATIC CONTROL APPARATUS Coleman B. Moore, Carroll Park, Pa., assignor to Moore Products Co., Philadelphia, Pa., a copartnership Application November 16, 1948, Serial No. 60,186

This invention relates -to pneumatic control apparatus and-'more particularly to apparatus which is responsive to the rate of application of fluid pressure applied thereto for applying a corrective factor for use in the control of other apparatus. v In accordance with -the present invention, provision is made for automatically Widening the throttling range dependent upon the rate of change of the applied fluid pressure of the measured variable.

In accordance with the present invention, also, control apparatus is provided which may be employed with 'pneumatic control systems having adjustable throttling ranges, with systems having either manual or automatic reset, or with systems having both an adjustable throttling range and reset.

The na-ture and characteristic features of the invention will :be more readily understood from the following description, taken in connection with the accompanying drawings forming part thereof, in which:

Figure 1 is a diagrammatic view of pneumatic control apparatus embodying an inverse derivative unit in accordance with the present invention;

Fig. 2 is a top plan view of a preferred form of control unit in accordance with the present invention;

Fig. 3 is a vertical central sectional view of the control unit shown in Fig. 2 and taken ap,- proximately on'the line 3-3 of Fig. 2;- and Fig. 4 is'afragmentary vertical sectional viewv taken approximately onthev line 4-4 of Fig. 2.

It should, ofcourse, be understood that the description and drawings herein are illustrative merely, and @that various modications and changes may be made in the structure disclosed without departing from the spirit of the invention.

Like numerals refer to like parts throughout the several views.

It has heretofore been proposed to apply a corrective effect' with a transmitted pressure which correctiveeffect is proportional to and greater 'than the transmitted pressure upon rapid changes in the'transmitted pressure but which becomes equal'to the transmitted pressure after the lapse of suiiiclent time. Such van e'ect has been'found of value in the control of processes with long time lags, and more particularly tem-- perature control.

Thev apparatus hereinafter described produces the inverse eiect in that the corrective action obtained upon arapid change in thetransmitted 7 Claims. (Cl. 137-485) 2 pressure is proportional `to but less than the transmitted pressure change, but which becomes equal to the transmitted pressure after the lapse of suflicient time. This apparatus is particularly suitable for providing stability in pneumatic con; trol systems in which the process variable changes faster than the control valve responds; l Referring now more particularly to Fig; l of the drawings, there is illustrated a pneumatic system which includes an inverse derivative unit I0, having a fluid transmitting connection II. for delivering air at a controlled pressure with a sub-tractive or additive effect superimposed upon an instrument pressure transmitted to the unit through a iiuid connection I2 from a control instrument such as an air controller I 3.

The control response setting up the instrument pressure transmitted by the controller I3 can be derived from iiow, pressure, or other variable which it is desired to control. The unit'II) lis illustrated as connected by a transmitting connection II to' a diaphragm valve I5, in a fluid flow line I4, although it could be used for the control of other apparatus. The unit I0 is illus-` trated also as having a fluid connection I6, from a source of pressure regulated and filtered iiuid, such as air, and which has a pressure regulator I'I interposed therein.

Referring now more particularly to Figs.` 2, 3 and 4 of thedrawings, the control uniti!) preferably lincludes a housing constructed'4 from a plurality of casing sections. The casing sections preferably consist of a top casing ,section 20; an upper casing section 2|, a lower casing section 2 2, and a bottom casing section 23, secured together in assembled relationship by studs 24; The top casing section 20 has the fluid connection I2 secured thereto and in communication with an interior chamber 25. Interposed between the top casing section 20 and the upper casing section 2l, a flexible diaphragm 26 is provided and clamped at its outer edges by the re spective casing sections 20 and 2 I.

The upper casing section 2| is provided in the interior thereof with a chamber 21 and has an inwardly extending ange28 for limiting the area of the lower face of the diaphragm 2B which is exposed to the pressure of uid in the chamber 21. The chamber 25 has a ring 29 mounted therein of the same internal diameter as the flange 28. The ring 2i! has a radial opening 30 therethrough in communication with a space 25a surrounding the chamber 25.

Interposed between the upper casing section 2| and the lower casingsection 22 andY bounding the chamber 21, a exible diaphragm 3l is provided and clamped at itsr outer edges by the respective casing sections 2| and 22. The lower casing section 22 is provided in the upper portion of the interior thereof with a chamber 32, bounded in part by the diaphragm 3|, so that the effective area of the lower face of the diaphragm 3|, exposed to the pressure in the chamber 32, is the same asthe effectivearea of the upper face of the diaphragm 3| exposed to the pressure in the chamber 21.

The diaphragms 26 and 3| are connected, for simultaneous movement, at the central portions thereof, by a connector sleeve 35 within which anV adjustable rod 36 is in threaded engagement. The rod 36 has a lower at control face 31, for purposes to be explained.

The lower casing section 22 has a detector nozzle 38 mounted therein, in communication with the chamber 32. The nozzle 38 has an oriflce which is controlled by the positioning with respect thereto of the control face v31.. Interposed between the lower casing section 22 and the bottom casing section. 23, a diaphragm assembly 4i! is provided having a porous central section 4| in radial communication with the atmosphere througha radial escape port 42, and controlling the positioning, with respect to a valve seat 430i a valve'seating member 44, carried on a valve stem 45, and interposed between the iuid.. supply connection |6 and the iluid transmitting connection The diaphragm assembly 40 and valve 44 may be of the character shown in my prior application` for Letters Patent for VPneumatic Control Apparatus, filed-December 22, 1945, Serial No. 637,057, now Patent No; 2,501,957 of March Y28, 195|).` A loading spring 46 is effective in a chamber-wat the undersideof the diaphragm` 40 and .a spring 41 is eiective against the valve member 44,7normal1y tending to urge it to seated position.. The upper end of. the. valve stem 45 isno-rmally seated in and closes a port. 49 in communication with the interior of -the diaphragm assembly 40.

It will benoted that the downstream side of the valve member d4 is in communication with the chamber 48 at the underside of the diaphragm assemblyv so that the transmittedpressure is effective thereagainst.- 1

l The-flower casing section 22 and the bottom casing-section 23 have afpassageway 50 therein for connecting together the uidsupply connection |6 Aand a chamber 56 with which Athe inlet side of the nozzle 38 is in communication. A restriction preferably of xed size, is.V provided -in the vpassageway 56. The pressure in the-chamber 56 is effective against the upper face of the diaphragm assembly 46.

The lower casing section. 22 and the bottom casing section. 23v have a vpassagewayl 52 therein for. connecting the fluid transmittingconnection |I to the chamber 32 sothat the transmitted pressure is effective in the chamber 32and against the lower face of the diaphragm 3|. v The-casing sections 25,'2I- and 22 are preferably provided with apassageway 53 which extends to an adjustable needlel valve `fi'fromthe chamber 25a, and the casing sections 22 and 2| are providedwith'a passageway-55 which-extendsfrom the needle valve 60 to the chamber 21'. -1 The needle valve 60 is preferably mounted in a valve sleeve `6| which -has a packing -62 for preventing fluid leakage and has a valve stem 63 'provided with a packing 64 `for preventing 4 fluid leakage. The outer end of the valve stem 63 is accessible from the exterior of the housing and is provided with an operating knob 65. Stops 66 and 61, respectively mounted on the casing section 22 and the knob 65, are provided to limit the extent of turning of the knob B5.

The mode of operation will now be pointed out.

It will be noted, that upon an increase in the instrument pressure supplied through the instrument connection I2, this increase in pressure is effective in the chamber 25 and against the upper face of the diaphragm 26. This tends to cause a downward movement of the diaphragm assembly, including the diaphragms 26 and 3|, and the control surface 31 is moved closer to the nozzle orifice 39. The decrease in ow through the nozzle orifice 39 is eifective, by the action of the diaphragm 40, to move the valve 44 farther from its seat 43, thus increasing the pressure in the .chambery 48 and transmitted through the fluid connection ll. The pressure of the ii'uid transmitted through the connection is also effective through the passageway 52 and in-'the chamber 32 and is eective upwardly Vagainst the diaphragm 3|, tending to restore the diaphragms 26 and 3| and the control surface 31 to a position of equilibrium. The pressure change required for such restoration is substantially less than that applied on the upper face of diaphragm 25 because of the difference in areas of the diaphragms 26 and 3|. f

The `increased pressure effective in the cham.- ber 25 will equalize by ilowing through the passageways 53. and 55 and past the needle valve 56 into the chamber 21. As such. equalization takes place the increase of pressure inv chamber 21 tends to move the diaphragm assembly downwardly vso as to decrease Vthe clearance between thecontrol face 31 andthe nozzle orifice 35. This Aaction causes an increase of pressure in chamber 25. as heretofore explained.

Upon completion of the equalization, the pressure in chamber 2'!V will equal that applied in chamber 25 and there will be no resultant force upon diaphragm 26. The pressure in chamber 32 will have been increased to equal thatv in chamber 21 and .therefore equal to the pressure in chamber 25.

Upon a decrease in the instrument pressure supplied through the instrument connection I2, a similar character of action will occur with a decrease in the transmitted pressure.- -mlt will be noted that any change in the instrument pressure through the .conduit l2 is effective inthe chamber 25 .to cause an immediate proportional change inthe pressure transmitted through the conduit ll, and that upon equalization of the pressure in the chambers 25 and 21, in accordance with the time determined by the setting of the needle valve 60, the total of the change applied at the conduit l2 becomes eective at the conduit Y I claim: .n

1. In pneumatic control apparatus, a control unit comprising a movable member having ya pluralityof pressure responsive faces of dineren-t pre-determined areas, means for applying on a smaller one of said'faces -a pressure from a variable source, a iluid connection in communication with said applying means and having a restriction therein for applying fluid pressure on a larger one of said faces in the same direction, asource of pressure regulated fluid, pressure transmitting means connected to said source and controlled vby positioning of `said movable member for transmitting a control pressure, and means for applying the control pressure on the movable member in opposition to the other pressures effective on said faces.

2. In pneumatic control apparatus, a control unit comprising a casing having a movable member therein with a plurality of pressure responsive faces of different pre-determined areas, means for applying on a smaller one of said faces a pressure from a variable source, a source of pressure regulated fluid, pressure transmitting means connected to said source and controlled by the positioning of said movable member for transmitting a control pressure, means for applying the control pressure on a larger one of said faces, and a fluid connection in communication With said applying means and having a variable restriction therein for applying fluid pressure on the faces opposite each of the other said faces.

3. In pneumatic control apparatus, a control unit comprising a movable member having a plurality of pressure responsive faces of different pre-determined areas, means for applying on a smaller one of said faces a pressure from a variable source, a fluid connection in communication with said applying means and having a restriction therein for applying fluid pressure on a larger one of said faces in the same direction, a source of pressure regulated fluid, pressure transmitting means connected to said source and controlled by positioning of said movable member for transmitting a control pressure and means a source of pressure regulated fluid, pressureV transmitting means connected to said source and controlled by positioning of said movable member for transmitting a control pressure, and means for applying the control pressure on a larger one of said faces in opposition to the pressures effective on said other faces.

5. In pneumatic control apparatus, a control unit comprising a casing having a plurality of' spaced coaxial diaphragms therein With pressure responsive faces, a member extendingbetween and connecting said diaphragms for movement in unison, means for applying on one of said diaphragm faces a pressure from a variable source, a uid connection in communication withsaid applying means for applying fluid pressure on another of said diaphragm faces in the same clirection, said fluid connection having a predetermined restricted passageway therein, a source of pressure regulated fluid, pressure transmitting means controlled by the positioning of said movable member and connected to said source of pressure regulated fluid for transmitting a control pressure, and means for applying the control pressure on one of the faces of said diaphragms in opposition to the other pressures effective on said diaphragms.

6. In pneumatic control apparatus, a control unit comprising a casing having therein a plurality of spaced coaxial diaphragms of different predetermined face areas, a member extending between and connecting said diaphragms for movement in unison, means for applying on a smaller one of said diaphragm faces a pressure from a variable source, a fluid connection in communication with said applying means for applying fluid pressure on a larger one of said diaphragm faces in the same direction, said fluid connection having a predetermined restricted passageway therein, a source of pressure regulated fluid, pressure transmitting means connected to said source of pressure regulated fluid and controlled by the positioning of said diaphragm for transmitting a control pressure, and means for applying the control pressure on one of the faces of said diaphragms in opposition to the other pressures effective on said diaphragms.

7.*In pneumatic control apparatus, a control unit comprising a movable member having a plurality of pressure responsive faces, means for applying on one of said faces a pressure from a variable source, a fluid connection in communication with said applying means and having a restriction therein for applying fluid pressure on another of said faces in the same direction, a source of fluid under pressure, pressure transmitting means connected to said sourceY for transmitting a control pressure, and means for applying the control pressure on said movable member on an area equal to the sum of the areas of said one and said other faces.

COLEMAN B. MOORE.

References cited in the me of this patent UNITED sTATEs PATENTS Number Name Date y 446,799 Thorpe Feb. 17, 1891 747,772 Rickman Dec, 22,v 1903 1,674,456 Smoot June 19, 1928 1,711,066 Smoot Apr. 30, 1929 1,865,105 Hauplain June 28, 1932 2,005,773 Florez June 25, 1935 2,232,219 Dueringer Feb. 18, 1941 Y2,286,282 Joesting June16, 1942 2,360,889 Philbrick Oct. 24, 1944 

